Impact wrench



Aug, 12, 1947. C, E, F11-CH 2,425,427

IMPACT WRENCH Filed DSC. 26, 1944 2 Sheets-Sheet 1 Fael 4 y ,44 n r y# Aug. 12, 1947. c. E. Fn-CH 2,425,427

IMPACT WRENCH Filed Dec. 26, l1944, 2 Sheets-Sheet 2 mmvzro @zy/@fd 222292, BY

Patented Aug. l2, 1947 IIVIPACT WRENCH fClitlord E. Fitch, Bryan, Ohio, assignor to The Aro Equipment Corporation, Bryan, Ohio, a

corporation of Ohio Application December as, 1944, Serial No. 569,671

1o claims. (ci. 19e-30.5)

My present invention relates to an impact wrench of the general character shown in my copending application, Serial No. 492,662, led June 29, 1943. I

One objectv of the present invention is to provide an impact wrench having hammer elements which are thrust outwardly by centrifugal force to deliver impact blows to an anvil element and which are movable'inwardly by means of link and cam connections when the driving means for the hammer elements moves ahead of the hammer elements following the delivery of an impact blow.

Another object is to arrange the parts so that there is substantially balanced pressure on them instead of pressure at the ends of the elements which would tend to cock them in relation to the other parts and thereby cause binding.

A further object is to provide an impact tool having a novel and compact impact delivery mechanism including a driving member, an anvil member and a hammer member, the hammer member being carried .by the driving member with a certain degree of st motion, and a link and cam connection being provided between the two to cause a retracting action of the hammer member at the proper time. V

Still a further object is to provide an impact delivering mechanism in which the parts can be readily renewed when worn and disassembly` and reassembly can be performed in a minimum of time and in a very simple manner.

With these and other objects in view, my` invention consists in the construction, arrangement and combination of the various parts of my device whereby the objects contemplated are at.-

l pacting mechanism and through it a wrench head.

, 2 Fig. 6 is a similar sectional view on the line 6-8 of Fig. 3;

Fig. 7 is a side elevation of the impacting mechanism looking at it in the same direction` as it is viewed in Fig. 5

Fig. 8 is anend view of one of the hammer elements;

Fig. 9 is a side elevation thereof looking in the direction of the arrow 9 adjacent Fig. 8; and

Fig. 10 is a face view of one of theretracting links for the hammer elements.

On the accompanying drawings I have used the reference character M to indicate a pneumatic motor for operating my impacty wrench. The motor M has a shaft I0 for driving the im- I 2. The wrench head I2 is removably mounted on a `wrench shaft I4 and may be replaced by wrench heads of other design for different size bolts or other devices to be turned by the wrench head.

sleeve I6 mounted in a casing C. The casing C is secured to the housing of the motor M as by threading or the like, and encloses the impacting mechanism shown in general in Figure 1. II'he impacting mechanism includes a driver I8 in the form of a shaft having a lreduced splined end 20 intertting with an internally splined sleeve 22. 'Ihe sleeve 22 is mounted on a splined portion 24 of the motor shaft I0. The forward end tained, as hereinafter more fully set forth, pointed .Fig. 3 is a similar sectional view showing the hammer members retracted and having cleared the anvil members and rotated to a further position than the position shown in Fig. 2;

Fig. 4 is a .sectional view on the line 4-4` of Fig. 1 showing an end view of the impacting assembly;

Fig. 5 is a sectional view on the line 5--5 of Fig. 3;

of the driver I8 has a socket 26 therein to receive an index pin 28 whichhas its forward end mounted in a socket 3U of the wrench shaft I4. The driver I8 is thereby supported on the index pin 30 at one end and on the motor shaft I0 at its a pair of striking faces 42. Between the striking,

faces 42 there are projections 44' which slidably enter the notches 36 of the discs 32. 'I'he openings 40 are formed in a pair of flanges 46 and receive pins 48. The pins 48 extend through the slots 34 of the discs 32 so that the pins and the projections 44 serve to guide the hammer elements H radially inward and outward, as shown in Figs.

'I'he wrenoh'shaft I4 is journaled in a bearing 3 2 and 3, respectively. In Fig. 4 thefhammer elements are also in their outerV position.

Mounted between the flanges 46 and o n the pins 48 is a pair of links 50 having cross-bars 52 and openings 54 in the ends of the links to receive the pins 48. The cross-bars 52 are on opposite sides of the driver I8, and the driver at this point is slotted in its opposite sides to provide a pair of at faces 56. These slots or notches in the driver and the flat faces 56 serve as cams with the edges of the slots indicated at 58 constituting the cam lobes, as will hereinafter appear.

The wrench shaft I4 has a disc-like portion'l) terminating in a pair of anvil elements 62 in the form of projections rearwardly from the plate. These projections are arcuate, as shown in Fig. 2, and have striking faces 64 in alignment with the striking faces 42 of the hammer elements H when they are in their outer position. The plates 32 are assembled in denitely spaced relation to each other by means of a pair of shouldered rivets 66, as shown in Figs. 5 and 7. The pins 48 have heads 68, and the pins are retained in assembled position by means of a washer-like plate mounted on the sleeve 22 against a shoulder 12 thereof.

Practical operation In the operation of my impact wrench, when the wrench head I2 is placed on a bolt, nut or the like, and the motor M supplied with actuating uid, such as compressed air, the motor rotates, which causes the driver I8 to rotate and the hammer elements H to move outwardly by centrifugal force to the position shown in Fig. 2.

As long as the bolt or nut will freely rotate, the wrench shaft i4 will be rotated simultaneously with the. motor shaft 24. When,.however, the

` resistance to turning torqueby the bolt or nut exceeds a predetermined point the anvil elements 62 will resist such rotation and permit the driver I 8 to move ahead of the assembly of plates 32, hammer elements H and links 58. This causes the cam lobes 58 to exert opposite pressure against the cross members 52 of the links, thereby tending to spread them, and this results in retracting the hammer elements as to the position shown in Fig. 3. As soon as retraction occurs sufficiently to permit the striking faces 42 to move out of alignment with the striking faces 64, the hammer elements will have released the impact elements and may rotate, as to the position of Fig. 3, withf out rotating the wrench shaft I4. As soon as the hammer elements pass the impact elements, centrifugal force will move them out again, as to the position of Fig. 4, and the motor will accelerate, thereby causing the forward striking face 42 in Fig. 4 to engage the anvil elements with impact. The number of impact blows may be determined by the length of time the motor is permitted to run, and the operator soon learns how long to let it run to get the nut or bolt tightened the desired degree.

My present disclosed impact mechanism is an improvement over the one shown in my copending application, Serial No. 492,662, filed June 29, 1943, in the use of a positive cam actuated means in the form of the cam 56-58 and the links 50,

instead of using the impact faces of the hammer and anvil elements as cams for this purpose. It is also an improvement from the standpoint of balancing the force applied between the various operating parts. The links 58 are substantially centered with relation to the lengths of the impact faces 42, thus eliminating any tendency toward cooking and resultant binding of the mer` elements with respect to the driver i8. The` arrangement of parts is also symmetrical to bal#- ance the'forces better, there being two of the elements and the links. 50 are symmetrical and so isthe cam 5658, so that the wrench can be operated in either direction with substantially the same performance in either direction. The motor M for this purpose is"made'reversible,v the reversing valve being shown at|,4. y

Some changes may be made inthe construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modied forms of structure or use of mechanical equivalents which may be reasonably included within their scope without sacricing any of the advantages thereof.

I claim as my invention:

1. In a tool of the character disclosed, relatively rotatable driving, anvil and hammer members and means for driving said hammer member from said driving member comprising a floating cage between said driving member and said anvil member. said hammer member being guided for substantially radial movement relative to said floating cage,a U-shaped link having its ends connected with said hammer member and its central cross-bar portion extending around said driving member on the opposite side `from said hammer member, said driving member having a depression adapted to receive said link and perf mit said hammer member 'to move outwardly from the center of rotation by centrifugal force,

whereupon its continued rotation results in the.

hammer member striking the anvil member to deliver an impact blow thereto and the hammer member being stopped in its rotation by the anvil member, said depression upon further rotation of said driving member pushing the cross-bar portion of said link away from the center and thereby pulling the hammer member toward the center and out of engagement with said anvil member to permit the hammer member to then rotatewith the driving member and, after passing the anvil member, move outwardly again by centrifugal force to strike another impact blow. 2. In a tool of the character described, a movable element, a rotary driving element therefor, a hammer. element arranged to be driven by said driving element and mounted for substantially radial movement relative to the axis of rotation thereof, said driving element having a cam lobe, said hammer element being located on one side of said driving element and having means on the opposite side thereof for engagement with said cam, whereby the cam lobe, upon the movement of the hammer element being stopped by the delivery of an impact blow to the anvil member, will result in radial movement inward of said hammer element to clear said anvil element upon the hammer element encountering resistance to torque greater than a predetermined degree.

3. In an impact wrench, a driver, a wrench and an operative connection between said driver and said wrench comprising an anvil carried by said wrench, a hammer element for driving said an vil and impact coacton therewith, said hammer element being carried by said driver and freely movable outwardly from the center of rotation thereof by centrifugal force to travel in a circular path and engage said anvil to impart rotation to said wrench simultaneously with the rotation of the driver untila predetermined resistance of the wrench to torque occurs, said driver thereupon retracting said hammer element inwardly toward the center of rotation to disengage it from the anvil to permit by-pass of the hammer element relative to the anvil and subsequent outward movement of the hammer element by centrifugal force to travel in said circular path and re-engage said anvil with impact, the retracting means comprising a cam carried by said driver and having a depressed portion, said hammer element being located on one side of said cam and having means on the opposite side of said cam normally seated in said depression and moved radially outward by an end of the depression upon engagement of said hammer element with said anvil and continued rotation of said driver ahead of said hammer.

4. An impact wrench comprising a driver, a wrench and an operative connection between the two comprising hammers having a slotted connection with said driver, said wrench having opposite projections constituting anvil elements for said hammers to impinge, whereby the hammers act as driving and impact elements in relation thereto, said hammers being movable outwardly from the center of rotation by centrifugal force to travel in a circle and ,engage said anvil projections to impart thereto simultaneous rotation in relation to the rotation of said driver and through intermittent impact of said hammers against said projections when resistance to torque rises to a predetermined degree, and means for releasing said hammers from said projections following delivery of the impact blows thereto comprising a cam and link connection between said driver and each of said hammers, said link connections being substantially U-shaped and being connected to said hammers at the extremities of the U.

5. In an impact wrench, a driver, a wrench and an operative connection between said driver and said wrench comprising a pair of hammers movable radially relative to said driver and on opposite sides thereof, said wrench having a pair of projections constituting anvil elements for said hammer elements to strike against whereby the hammer elements act as driving and impact means in relation thereto, said hammer elements being freely movable in slots of said driver and being thrust outwardly by centrifugal force to travel in a path coincident with said anvil projections to impart rotation thereto, or through intermittent impact thereagainst when resistance to torque rises to a predetermined degree thereby imparting rotation by impact blows, and retracting means for said hammer elements comprising U-shaped links connected therewith and located in opposite slots of the shaft of said driver.

6. In a rotary impact tool having a hammer driving member, an anvil and a hammer for striking the anvil, said hammer being guided for movement inwardly and outwardly relative to the axis of rotation, said hammer driving member being movable outwardly :by centrifugal force so as to cause simultaneous rotation of the anvil with the hammer, said hammer and anvil disengageably cooperable with each other upon predetermined driving torque of the hammer driving member in excess of resistance to turning torque by the work through the anvil, cam means for effecting such disengagement' and links for said hammer elements cooperating with said cam means to cause the disengagement after which said hammer is centrifugally moved outwardly until again contacting the anvil and delivering an impact blow thereto, said links being substantial- 1y U-shaped and being connected to said hammers at the extremities of the U.

7. In a tool of the character described, a rotary driving element and a rotatable driven element, said driven element having an avil, a hammer element carried by said driving element and movable outwardly from the axis of rotation thereof to engage said anvil element, and a connection between said ldriving element and said hammer element comprising a link around the opposite sidev of the driving element from said hammer element and cooperating with a slot cut in the driving element and constituting a cam for retracting the hammer element relative to the anvil element.

`8. In an impact wrench structure, a driver,

means for rotating said driver, a wrench shaft having oppositely disposed anvil elements, radially movable hammer elements for coaction therewith, a pair of plates fioatingly mounted on said driver and having said hammer elements guided thereby for radial movement, and U- shaped links mounted between said plates and having their ends connected with said hammer elements, said driver having a cam provided with opposite depressions and intermediate lobes, the cross-bars of said links being positioned on opposite sides thereof whereby rotation of said driver relative to said plates will move said link cross-bars apart and thereby retract said hammer elements.

9. An impact mechanism comprising a driver, a pair of discs rotatable thereon, a pair of hammer elements having slotted connection therewith for radial movement of the hammer elements, a pair of anvil elements, a tool driven thereby, said hammer elements being engageable with said anvil elements when the hammer elements are in outward positions due to centrifugal force, and cam and link connections between said driver and said hammer elements for retracting said hammer elements when said driver overruns said discs and hammer elements,

. said link connections being substantially U- shaped and being connected to said hammers at the extremities of the U.

10. In an impact wrench structure, a drive shaft, means for rotating said drive shaft, a wrench shaft having oppositely disposed anvil elements, radially movable impact hammer elements for coaction therewith, a pair of plates fioatably mounted on said drive shaft and having said hammer elements guided thereby for radial movement, and U-shaped links including cross-bars mounted between said plates and having their ends connected to said hammer elements, said drive shaft having opposite notches with the cross-bars of said links therein on opposite sides of said drive shaft, whereby rotation of said drive shaft relative to said plates moves said cross-bars apart to retract said hammer elements from said anvil elements.

CLIFFORD E. FITCH.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,285,638 Amtsberg June 9, 1942 2,326,347 Forss Aug. 10, 1943 2,343,332 Shai Mar. 7, 1944 

